Train won't automate in tutorial mission - "No path"

[THX11384EB]

I am playing the tutorial where the player first encounters trains. There are no instructions on how to place stops but it doesn't seem to make a difference whether I place it at either end of where I want the train to stop; I get "no path". Even though the path is clear, repaired and I can move the train manually. There is only one train on the track; it's a simple track with two ends. I see people talking about signals but there are no instructions on how to place signals and the tutorials I've watched didn't even both placing any signals in any case (I think they might only be needed for multiple trains on the same track). The train does automate in one direction, but then I have to manually drive it back up which defeats the object.

[Loewchen]

The stop is on the wrong side of the track.